Active matrix substrate and display device including the same

Abstract

The thickness of a rear surface-side inorganic film ( 9 ) formed from the same material as that of each of front surface-side inorganic films ( 11, 13 , and 16 ) and provided at a rear surface side of a resin substrate ( 10 ) having a heat resistance is set in a predetermined range with respect to the total thickness of the front surface-side inorganic films ( 11, 13 , and 16 ) so that the curvature diameter calculated based on the linear elastic modulus, the coefficient of linear expansion, and the thickness of the resin substrate ( 10 ); the linear elastic moduli, the coefficients of linear expansion, and the total thickness of the front surface-side inorganic films ( 11, 13 , and 16 ); and the linear elastic modulus, the coefficient of linear expansion, and the thickness of the rear surface-side inorganic film ( 9 ) is 20 mm or more or −20 mm or less.

The invention claimed is: 
     
       1. An active matrix substrate comprising:
 a resin substrate having a heat resistance; 
 a thin film electrical element provided at a front surface side of the resin substrate; 
 a plurality of front surface-side inorganic films which are formed from the same material and which are provided as different layers from each other at the front surface side of the resin substrate; and 
 a rear surface-side inorganic film which is formed from the same material as that of each of the front surface-side inorganic films and which is provided at a rear surface side of the resin substrate, wherein 
 the thickness of the rear surface-side inorganic film is set in a predetermined range with respect to the total thickness of the plurality of front surface-side inorganic films so that the curvature diameter calculated based on the linear elastic modulus, the coefficient of linear expansion, and the thickness of the resin substrate; the linear elastic moduli, the coefficients of linear expansion, and the total thickness of the plurality of front surface-side inorganic films; and the linear elastic modulus, the coefficient of linear expansion, and the thickness of the rear surface-side inorganic film is 20 mm or more or −20 mm or less, 
 the resin substrate is formed of a polyimide resin, 
 the front surface-side inorganic films are each a silicon nitride film, and 
 when the total thickness of the plurality of front surface-side inorganic films is represented by X a  μm, a thickness Y a  μm of the rear surface-side inorganic film satisfies the following relational expression
   −0.1263 X   a   2 +0.674 X   a +0.0733≦ Y   a ≦25.321 X   a   3 −49.8 X   a   2 +34.76 X   a −7.355.
 
 
 
     
     
       2. The active matrix substrate according to  claim 1 ,
 further comprising a front surface-side resin film for planarizing a substrate surface at the front surface side of the resin substrate. 
 
     
     
       3. The active matrix substrate according to  claim 2 ,
 further comprising a rear surface-side resin film having a heat resistance at the rear surface side of the resin substrate, 
 wherein the thickness of the rear surface-side resin film is set in a predetermined range with respect to the thickness of the front surface-side resin film so that the curvature diameter calculated based on the linear elastic modulus, the coefficient of linear expansion, and the thickness of the resin substrate; the linear elastic moduli, the coefficients of linear expansion, and the total thickness of the plurality of front surface-side inorganic films; the linear elastic modulus, the coefficient of linear expansion, and the thickness of the rear surface-side inorganic film; the linear elastic modulus, the coefficient of linear expansion, and the thickness of the front surface-side resin film; and the linear elastic modulus, the coefficient of linear expansion, and the thickness of the rear surface-side resin film is 20 mm or more or −20 mm or less. 
 
     
     
       4. The active matrix substrate according to  claim 3 ,
 wherein the front surface-side resin film is formed from an acrylic resin to have a thickness of X b  μm, 
 the rear surface-side resin film is formed from a polyimide resin to have a thickness of Y b  μm, and 
 when the total thickness of the resin substrate, the front surface-side inorganic films, and the rear surface-side inorganic film is represented by X c  μm, the thickness Y b  of the rear surface-side resin film satisfies the following relational expression
   (−0.045 X   b   2 +1.4939 X   b −1.9462)(−0.0348 X   c   2 +0.1518 X   c +1.4817)≦ Y   b ≦(0.0173 X   b   2 +0.8303 X   b +1.4109)(0.0073 X   c   2 −0.0011 X   c +0.7038).
 
 
 
     
     
       5. The active matrix substrate according  claim 1 ,
 wherein the thin film electrical element is a thin film transistor including a gate electrode and a semiconductor layer, and 
 the plurality of front surface-side inorganic films includes an underlayer film provided on the front surface of the resin substrate, a gate insulating film provided between the gate electrode and the semiconductor layer, and a protective film provided so as to cover the thin film transistor. 
 
     
     
       6. The active matrix substrate according  claim 1 ,
 wherein the resin substrate has transparency. 
 
     
     
       7. The active matrix substrate according to  claim 3 ,
 wherein the front surface-side resin film and the rear surface-side resin film each have transparency. 
 
     
     
       8. A display device comprising:
 the active matrix substrate according to  claim 1 ; 
 a counter substrate provided to face a front surface side of the active matrix substrate at which the thin film electrical element is provided; and 
 a display medium layer provided between the active matrix substrate and the counter substrate. 
 
     
     
       9. The display device according to  claim 8 ,
 wherein the display medium layer is a liquid crystal layer. 
 
     
     
       10. An active matrix substrate comprising:
 a resin substrate having a heat resistance; 
 a thin film electrical element provided at a front surface side of the resin substrate; 
 a plurality of front surface-side inorganic films which are formed from the same material and which are provided as different layers from each other at the front surface side of the resin substrate; and 
 a rear surface-side inorganic film which is formed from the same material as that of each of the front surface-side inorganic films and which is provided at a rear surface side of the resin substrate, 
 wherein the thickness of the rear surface-side inorganic film is set in a predetermined range with respect to the total thickness of the plurality of front surface-side inorganic films so that the curvature diameter calculated based on the linear elastic modulus, the coefficient of linear expansion, and the thickness of the resin substrate; the linear elastic moduli, the coefficients of linear expansion, and the total thickness of the plurality of front surface-side inorganic films; and the linear elastic modulus, the coefficient of linear expansion, and the thickness of the rear surface-side inorganic film is 20 mm or more or −20 mm or less, 
 the active matrix substrate further includes a front surface-side resin film for planarizing a substrate surface at the front surface side of the resin substrate, and a rear surface-side resin film having a heat resistance at the rear surface side of the resin substrate, 
 the thickness of the rear surface-side resin film is set in a predetermined range with respect to the thickness of the front surface-side resin film so that the curvature diameter calculated based on the linear elastic modulus, the coefficient of linear expansion, and the thickness of the resin substrate; the linear elastic moduli, the coefficients of linear expansion, and the total thickness of the plurality of front surface-side inorganic films; the linear elastic modulus, the coefficient of linear expansion, and the thickness of the rear surface-side inorganic film; the linear elastic modulus, the coefficient of linear expansion, and the thickness of the front surface-side resin film; and the linear elastic modulus, the coefficient of linear expansion, and the thickness of the rear surface-side resin film is 20 mm or more or −20 mm or less, 
 the front surface-side resin film is formed from an acrylic resin to have a thickness of X b  μm, 
 the rear surface-side resin film is formed from a polyimide resin to have a thickness of Y b  μm, and 
 when the total thickness of the resin substrate, the front surface-side inorganic films, and the rear surface-side inorganic film is represented by X c  μm, the thickness Y b  of the rear surface-side resin film satisfies the following relational expression
   (−0.045 X   b   2 +1.4939 X   b −1.9462)(−0.0348 X   c   2 +0.1518 X   c +1.4817)≦ Y   b ≦(0.0173 X   b   2 +0.8303 X   b +1.4109)(0.0073 X   c   2 −0.0011 X   c +0.7038).
 
 
 
     
     
       11. The active matrix substrate according to  claim 10 ,
 wherein the thin film electrical element is a thin film transistor including a gate electrode and a semiconductor layer, and 
 the plurality of front surface-side inorganic films includes an underlayer film provided on the front surface of the resin substrate, a gate insulating film provided between the gate electrode and the semiconductor layer, and a protective film provided so as to cover the thin film transistor. 
 
     
     
       12. The active matrix substrate according to  claim 10 ,
 wherein the resin substrate has transparency. 
 
     
     
       13. The active matrix substrate according to  claim 10 ,
 wherein the front surface-side resin film and the rear surface-side resin film each have transparency. 
 
     
     
       14. A display device comprising:
 the active matrix substrate according to  claim 10 ; 
 a counter substrate provided to face a front surface side of the active matrix substrate at which the thin film electrical element is provided; and 
 a display medium layer provided between the active matrix substrate and the counter substrate. 
 
     
     
       15. The display device according to  claim 14 ,
 wherein the display medium layer is a liquid crystal layer.